1. Field of the Invention
The present invention relates to a slurry to be used for CMP (Chemical Mechanical Polishing), a polishing method using the slurry, and a method of manufacturing a semiconductor device.
2. Description of the Related Art
It is expected that the integration of semiconductor elements in high-performance LSIs of the next generation will be inevitably further enhanced. For example, the design rule of damascene wirings to be formed by CMP is expected to become so severe that the line width of wirings is will be confined within the range of 0.07 to 30 μm and the film thickness of wirings will be confined to not more than 100 nm.
Therefore, in designing a slurry for CMP, it is required to take these conditions into account and to employ abrasive grains which are sufficiently small relative to the line width of wirings so as to make it possible to perform fine and delicate polishing. For example, there has been proposed employing a slurry comprising two or more colloidal silica whose primary particle diameter is controlled. These slurries are capable of polishing a polishing surface while suppressing the generation of erosion and scratching if the polishing surface is constituted of a soft material or by a sole material, thereby enabling these slurries to exhibit excellent CMP performances. However, if the polishing surface is constituted of a hard material such as Ta or SiO2, these slurries are incapable of performing the polishing at a sufficiently high polishing speed. Further, there is a problem that if the polishing surface is constituted of two or more materials, it is difficult to adjust the polishing balance so as to enable plural materials to be polished at the same polishing rate as each other.